1. An experimental pneumonia with more or less lobar distribution has been produced in dogs by the method of intrabronchial insufflation of B. friedlænderi, Type B, and Pneumococcus, Type I.
2. Such dogs as showed evidences of a pulmonary lesion when photographed by x-ray were selected for lung temperature measurements.
3. Measurements of lung temperature were made by means of thermocouples before and during diathermy.
4. The thermocouples which recorded the temperature in the consolidated lobes showed in most instances a more rapid rate of heating during diathermy than those in the normal lobes. The final increase in temperature in the pathological lobes over the normal lobes amounted to slightly more than 1°C.
5. When local heating occurred during diathermy it was of the order of magnitude found in a lung in which the branch of the pulmonary artery supplying it had been clamped.
6. Histological examination of the lungs showed the pathological reaction to consist of intraalveolar exudate composed of polymorphonuclear leucocytes and desquamated alveolar epithelium. In some sections the exudate was sufficient to cause compression and emptying of the alveolar capillaries.
7. The local heating, we believe, depends upon this ischemic state of the smaller vessels.
8. Further evidence for an imparied circulation in the pneumonic lung is furnished by injection preparations in which the uninjected area corresponded exactly to the gross pathological lesion.